An ultrasonic diagnosis apparatus is a medical equipment for obtaining an ultrasound image of a target region in an object so as to provide clinical information of the target region, such as lesion or neoplasm information of internal organs, fetus information and the like. Typically, the ultrasonic diagnosis apparatus comprises at least one probe having an ultrasound element assembly for radiating the ultrasonic wave to the target region and receiving the echo signal reflected from the target region. Recently, to obtain more accurate diagnosis, there have been developed techniques for acquiring a 3-dimensional (3D) ultrasound image by pivoting the ultrasound element assembly of the probe.
Japanese Patent Application Publication No. 2002-153464 discloses a prior art probe of a 3D ultrasonic diagnosis apparatus, which will be described with reference to FIGS. 1A and 1B. FIG. 1A is a partial cross-sectional view showing an inner structure of a prior art probe for acquiring a 3D ultrasound image. FIG. 1B is a side view showing a power transmitting structure of a prior art probe.
As shown in the drawings, a prior art probe 1 comprises a case 10 having an opened top and a cover 12, which is coupled to the opened top of the case 10 and is adapted to contact an object to be examined (e.g., a body of a patient). Abase 20 is contained in the case 10. A transducer 30 for supporting an ultrasound element assembly (not shown) is pivotably mounted to the base 20 by a pivot shaft 32. A driving motor 40 for generating power necessary for pivoting the transducer 30 and means for transmitting the power from the motor 40 to the pivot shaft 32 are mounted to the base 20.
The pivot shaft 32 is arranged horizontally and is rotatably coupled to the base 20 by bearings 34 at both ends of the shaft 32. Preferably, the driving motor 40 is a step motor and is mounted to an outer surface of the base 20. A driving shaft 42 of the motor 40 is inserted horizontally into the base 20 and supported by a bearing 44 at its end.
In order to transmit the power from the motor 40 to the pivot shaft 32, a driving pulley 46 is coupled to the driving shaft 42 for rotation with the shaft 42. A driven pulley 48 is coupled to the pivot shaft 32 for rotation with the shaft 32. The driving pulley 46 and the driven pulley 48 are arranged in alignment with each other and are connected by a driving belt 49. Preferably, the driving belt 49 is a flat strip having a rectangular cross-section.
When the driving pulley 46 rotates in a direction of arrow A depicted in FIG. 1B by the operation of the driving motor 40, the driven pulley 48 also rotates in a direction of arrow A by the driving belt 49. On the contrary, when the driving pulley 46 rotates in a direction of arrow B, the driven pulley 48 rotates in a direction of arrow B by the driving belt 49. Accordingly, the pivot shaft 32, to which the driven pulley 48 is coupled, and the transducer 30 supporting the ultrasound element assembly can be pivoted within a predetermined angle.
However, during the pivoting operation, the pulleys and the belt may slip, which hinders the driving force of the motor from being transmitted perfectly to the transducer. Further, since the operational vibration of the motor directly affects the transducer through the belt, the ultrasonic wave is radiated irregularly and the 3D ultrasound image may not be optimal. Thus, the image quality is degraded, which causes an erroneous diagnosis.
Also, the driving belt may get loosened due to the repeated operations, which makes it impossible to conduct the precise pivoting of the transducer. Although an additional belt tensioning means may be provided in the probe to solve this problem, the limited size of the probe imposes many limitations upon installing the belt tensioning means.